Water-soluble or water-swellable, associatively thickening copolymers containing sulfo groups, method for producing the same and use thereof

ABSTRACT

The invention relates to water-soluble or water-swellable copolymers which contain sulfo groups and which are based on (meth)acrylamide-alkylsulfonic acids and (meth)acrylamide or N-vinyl compounds, and to their use as additives for aqueous construction materials systems or for water-based paint and coating systems. The inventive copolymers also represent water retention agents which are highly effective, even when used in relatively small quantities, and which are highly compatible in construction material and paint systems of this type.

This application is a U.S. National Phase of PCT/EP01/08938 filed Aug.2, 2001, incorporated herein by reference in its entirety.

The present invention relates to water-soluble or water-swellable,associatively thickening copolymers containing sulfo groups, methods forproducing the same and the use of these copolymers in aqueousconstruction-material systems based on hydraulic binders, such ascement, lime, gypsum, anhydrite, etc., or else in water-based paintsystems and water-based coating systems.

Aqueous construction-material mixtures usually use water-solublenon-ionic derivatives of polysaccharides, in particular cellulosederivatives and starch derivatives, in order to delay or prevent theundesirable evaporation of the water required for hydration and use, orthe escape of this water into the ground.

The ability to control the water balance in paint systems, renders,adhesive mortars, troweling compounds and joint fillers, and also inspray concretes or tunnel construction and in underwater concretes byusing these additives has wide-ranging practical consequences.Specifically, it has a decisive effect both on the properties of theconstruction material in its usage condition and on its properties inthe hardened or dried condition. Through the central function of waterretention, therefore, these additives also affect consistency(plasticity), open time, smoothability, segregation, tack, adhesion (tothe ground and to the tooling), mechanical stability, and slipresistance, and also tensile bond strength and compressive strength orshrinkage.

According to Ullmann's Enzyklopadie der Technischen Chemie (4^(th)edition, Volume 9, pages 208-210, Verlag Chemie Weinheim), the mostcommonly used water-retention agents are synthetically producednon-ionic derivatives of cellulose and of starch, for example methylcellulose (MC), hydroxyethyl cellulose (HEC), hydroxyethylmethylcellulose (HEMC). However, use is also made of microbially producedpolysaccharides, such as Welan gum, and naturally occurring extractivelyisolated polysaccharides (hydrocolloids), such as alginates, xanthans,caragheenans, galactomannans, etc., and these are used in the prior artto regulate the water balance and the rheology of aqueousconstruction-material systems and aqueous paint systems.

A disadvantage with these products is the use, in the productionprocess, of raw materials which are known to be physiologicallyhazardous, for example ethylene oxide, propylene oxide, and methylchloride.

A number of publications, such as DE-A 39 34 870, describe the use ofnon-ionic cellulose derivatives in the construction-material and paintsector. These products have low thermal flocculation points, the resultbeing a drastic reduction in water-retention ability at temperaturesabove 30° C. The rheological property profile of these products ismoreover inadequate in paint systems, since the additives provideinsufficient adsorptive forces to disperse the pigments. These problemscan be solved by using cellulose ethers which contain ionic groups.

For example U.S. Pat. No. 5,372,642 describesmethylhydroxyalkylcarboxymethylcelluloses which in lime- andcement-containing mixtures give no fall-off in water retention when theusage temperature is increased from 20 to 40° C.

U.S. Pat. No. 5,863,975 moreover describes synthetic polymers which havewater-retention properties and contain monomers containing carboxylgroups, for example acrylic acid. Due to the carboxylate groups, they,like the methylhydroxyalkylcarboxymethylcelluloses, markedly delayhardening in hydraulic binders.

In addition, there is a possibility of general incompatibility withpolyvalent cations, such as Ca²⁺ and Al³⁺, and this can lead toflocculative precipitation and thus to ineffectiveness of theseproducts.

Sulfoalkylated cellulose derivatives are described in EP-A 554 749,inter alia. They, like the polyelectrolytes according to DE-A 198 06 482containing sulfo groups, have excellent compatibility with polyvalentcations, when compared with products containing carboxy groups.

However, unlike the polymers according to DE-A 198 06 482 containingsulfo groups, the sulfoalkylated cellulose derivatives exhibit markedsetting-delay properties when used in adhesive mortars and renders.

The polyelectrolyte properties of all long-chain ionic polymers, whethercellulose-based or synthetically prepared, bring about high viscositiesin solutions with low salt concentration. If, however, the salt contentis higher the viscosity falls away markedly.

The following problem arises specifically in construction-materialmixtures which comprise hydraulic binders and other ionic additives: ifthe construction-material mixtures which comprise these polyelectrolytesare freshly mixed the resultant viscosity is high. After an aging periodof from 5 to 10 min, the high salt concentration in the aqueous phase ofthe mixed construction-material mixture brings about a fall inviscosity. In adhesive mortars, these products give inadequatemechanical stability, in particular when the tiles used are heavy. Inaddition, a significant requirement of the user of these products isconstant usage consistency over a realistic usage period.

Another disadvantage of construction-material systems containingpolyelectrolyte is the incompatibility and destabilization of theair-pore formers present in the construction-material systems (renders).It is therefore impossible to produce products with high air-porecontent, e.g. renders for restoration work, since the usage propertiesrequired are greatly dependent on air-pore content and air-poredistribution.

Other difficulties with the polyelectrolytes according to DE-A 198 06482 containing sulfo groups arise in preparing the polymers in the formof gel polymers. Polymerization using gel polymerization technologymostly gives a gel block which has to be comminuted to permit effectivedrying of the polymer.

For the gel block to be capable of comminution, the consistency of thegel block is very important. Only if the chain lengths are very high isthe gel sufficiently hard to permit cutting of the gel block. Otherwise,comminution is possible only with great difficulty and at high technicalcost.

Even in combination with a release agent, the gel granules produced tendto cake, making further processing (conveying and drying) problematic.Gel polymerization technology can be used only with difficulty and athigh technical cost.

The present invention was therefore based on the object of developingwater-soluble or water-swellable copolymers which do not have thedisadvantages mentioned of the prior art, but are effective even atcomparatively high temperatures, and exhibit properties which giveconstant thickening even at high electrolyte content, and also can beproduced by a simple method with good reproducibility by the gelpolymerization method, and moreover give the construction-materialsystems and paint systems excellent performance characteristics duringusage and in the hardened or dried state.

According to the invention, this object has been achieved by way of thecopolymers corresponding to claim 1.

Indeed, it has surprisingly been found that the copolymers of theinvention are highly effective water-retention agents with goodcompatibility in construction-material systems and paint systems, evenwhen the amounts used are relatively small, and together with this haveimproved properties when compared with products currently used.Furthermore, the amphiphilic character of the polymers and thehydrophobicized side chains permit a marked improvement in waterretention and controlled adjustment of thickening properties. Even athigh salt concentrations, it is possible to achieve a realisticconsistent usage consistency. These effects, too, were certainly notpredictable.

The copolymers of the present invention are composed of at least fourunits a), b), c), and d). The first unit is a substituted acrylic ormethacrylic derivative containing sulfo groups and having the formula I:

where R¹=hydrogen or methyl, R², R³, R⁴=hydrogen, an aliphatichydrocarbon radical having from 1 to 6 carbon atoms, a phenyl radicalwhich is unsubstituted or substituted with from 1 to 5, preferably up to3, methyl groups, and M=hydrogen, a mono- or divalent metal cation,ammonium, or an organic amine radical, and a=½ or 1. The mono- ordivalent metal cation used is preferably alkali metal ions or/andalkaline earth metal ions and in particular sodium ions, potassium ions,calcium ions, or magnesium ions. The organic amine radicals used arepreferably substituted ammonium groups which derive from primary,secondary, or tertiary amines having C₁-C₂₀-alkyl, C₁-C₂₀-alkanol,C₅-C₈-cycloalkyl, or/and C₆-C₁₄-aryl radicals. Examples of appropriateamines are methylamine, dimethylamine, trimethylamine, ethanolamine,diethanolamine, triethanolamine, cyclohexylamine, dicyclohexylamine,phenylamine, and diphenylamine, each of which in the protonated ammoniumform provides an organic amine radical as radical M of the invention.

The unit a) derives from monomers such as2-acrylamido-2-methylpropanesulfonic acid,2-methylacrylamido-2-methylpropanesulfonic acid,2-acrylamidobutanesulfonic acid, 3-acrylamido-3-methylbutanesulfonicacid, 2-acrylamido-2,4,4-trimethylpentanesulfonic acid.2-Acrylamido-2-methylpropanesulfonic acid is particularly preferred.

The second unit b) corresponds to the formula IIa) and/or IIb):

where W=—CO—, —CO—O—(CH₂)_(x)—, —CO—NR²—(CH₂)_(x)—

-   -   x=from 1 to 6 and    -   R¹ and R² are as defined above.

-   R⁵ and R⁶ are, independently of one another, hydrogen, an aliphatic    hydrocarbon radical having from 1 to 20 carbon atoms, a    cycloaliphatic hydrocarbon radical having from 5 to 8 carbon atoms,    or an aryl radical having from 6 to 14 carbon atoms. Where    appropriate, these radicals may have substitution with hydroxyl,    carboxyl, or sulfonic acid groups.

-   Q in formula IIb) is hydrogen or —CHR⁵R⁷. If Q≠H, R⁵ and R⁶ in    structure IIb) may also together be a —CH₂—(CH₂)_(y)-methylene    group, where y=from 1 to 4, and these form a five- to eight-membered    heterocyclic ring when the remainder of the formula IIb) is included

-   R⁷ may be a hydrogen atom, a C₁-C₄-alkyl radical, a carboxylic acid    group, or a carboxylate group —COOM_(a), where M and a are as    defined above.

Preferred monomers which may be used and have the structure IIa) are thefollowing compounds: acrylamide, methacrylamide, N-methacrylamide,N,N-dimethylacrylamide, N-ethylacrylamide, N-cyclohexylacrylamide,N-benzylacrylamide, N-methylolacrylamide, N-tert-butylacrylamide, etc.Examples of monomers on which the structure IIb) is based areN-methyl-N-vinyl-formamide, N-methyl-N-vinylacetamide,N-vinylpyrrolidone, N-vinyl-caprolactam, N-vinylpyrrolidone-5-carboxylicacid, etc.

The third unit c) corresponds to the formulae IIIa and/or IIIb

where Y=O, NH or NR⁵

-   -   V=—(CH₂)_(x)—,

-   -   R⁸=R⁵ or R⁶, —(CH₂)_(x)—SO₃ ⁻(M),

-   -   X=halogen, (preferably Cl, Br), C₁-C₄-alkyl sulfate (preferably        methyl sulfate) or C₁-C₄alkylsulfonate and    -   R¹, R², R³, R⁵, R⁶, and x are as defined above.

Examples of preferred monomers which may be used and form the structure(IIIa) are: [2-(acryloyloxy)ethyl]trimethylammonium chloride,[2-(acryloylamino)ethyl]trimethylammonium chloride,[2-(acryloyloxy)ethyl]trimethylammonium methosulfate,[2-(methacryloyloxy)ethyl]trimethylammonium chloride or methosulfate,[3-(methacryloylamino)propyl]trimethyl-ammonium chloride,N-(3-sulfopropyl)-N-methacryloxyethyl-N′-N-dimethylammonium betaine,N-(3-sulfopropyl)-N-methyacrylamidopropyl-N,N-dimethylammonium betaine,and 1-(3-sulfopropyl)-2-vinylpyridinium betaine.

Examples of monomers on which the structure IIIb is based areN,N-dimethyldiallylammonium chloride and N,N-diethyldiallylammoniumchloride.

The fourth unit d) corresponds to the formula IV

where Z=—COO(C_(m)H_(2m)O)_(n)—R⁹, —(CH₂)_(p)—O(C_(m)H_(2m)O)_(n)—R⁹

-   -   or else a saturated or unsaturated, linear or branched,        aliphatic hydrocarbon radical having from 22 to 40 carbon atoms

-   R¹⁰=H, C₁-C₄-alkyl-, phenyl-, benzyl-, C₁-C₄-alkoxy, halogen (F, Cl,    Br, I), cyano, —COOH, —COOR⁵, —CO—NH₂, —OCOR⁵

-   R¹¹=arylalkyl group having a C₁-C₁₂-alkyl radical and C₆-C₁4-aryl    radical

-   m=from 2 to 4

-   n=from 0 to 200

-   p=from 0 to 20    and R¹ and R⁵ are as defined above.

Preferred monomers which form the structure IV are tristyrylpolyethyleneglycol 1100 methacrylate, behenylpolyethylene glycol 1100 methacrylate,tristyrylpolyethylene glycol 1100 acrylate, tristyrylpolyethene glycol1100 monovinyl ether, behenylpolyethene glycol 1100 monovinyl ether,phenyltriethylene glycol acrylate, tristyrylpolyethylene glycol 1100vinyloxybutyl ether, behenylpolyethylene glycol 1100 vinyloxybutylether, tristyrylpolyethylene glycol-block-propylene glycol allyl ether,behenylpolyethylene glycol-block-propylene glycol allyl ether, etc.

It is important for the invention that the copolymers are composed offrom 3 to 96 mol % of the unit a), from 3 to 96 mol % of the unit b),and from 0.05 to 75 mol % of the unit c), from 0.01 to 30 mol % of theunit d). Polymers whose use is preferred contain from 40 to 80 mol % ofa), from 15 to 55 mol % of b), from 2 to 30 mol % of c), and from 0.3 to10 mol % of d).

The number of structural repeat units in the copolymers of the inventionis unrestricted and is very highly dependent on the respectiveapplication sector. However, it has proven advantageous to adjust thenumber of structural units so that the copolymers have a number-averagemolecular weight of from 50 000 to 20 000 000, preferably from 500 000to 10 000 000, in particular up to 8 000 000.

The copolymers of the invention are prepared in a manner known per se byusing free-radical, ionic, or complex-coordinative bulk, solution, gel,emulsion, dispersion or suspension polymerization to link the monomersforming the structures a) to d). Since the products of the invention arewater-soluble copolymers, preference is given to polymerization in theaqueous phase, polymerization in inverse emulsion or polymerization ininverse suspension. In a particularly preferred embodiment, the reactionis a gel polymerization or an inverse suspension polymerization inorganic solvents.

If the process is carried out in an aqueous phase, gel polymerization ispreferred, especially for the preparation of copolymers in the uppermolecular-weight range (e.g. ≧1 000 000, in particular ≧10 000 000 Da),these being the materials used in adhesive mortars and in underwaterconcrete, for example. The use of the monomers derived from the unit d)dramatically improves the ease of comminuting and processing the gel,even at low degrees of polymerization, and gel polymerization istherefore the preferred embodiment, for reasons of cost-effectiveness.

Solution polymerization is less cost-effective due to extremely highsolution viscosities of these high-molecular-weight products and thehigh resultant cost. However, the preparation of copolymers of theinvention whose molecular weight is in the lower or central range (e.g.up to 5 000 000 Da) (useful in flowable screeds as anti-segregationagents and thickeners in paint systems) may in contrast readily take theform of an aqueous solution polymerization.

The monomers are reacted here in particular at temperatures of from −20to 250° C., at a concentration of from 5 to 20% by weight, and at a pHof from 4 to 9. The polymerization preferably takes place at from 5 to120° C. with the aid of conventional free-radical initiators, such ashydrogen peroxide, sodium peroxodisulfate, potassium peroxodisulfate, orammonium peroxodisulfate, dibenzoyl peroxide,2,2′-azobis(2-amidinopropane) dihydrochloride,azobis(isobutyronitrile)tert-butyl hydroperoxide, or by a physical routevia irradiation, or electrochemically. It is also possible to combinethe abovementioned initiators with reducing agents, such as dibutylaminehydrochloride, Na hydroxymethanesulfinate dihydrate, alkali metalsulfites and alkali metal metabisulfites, thiourea, transition metalsalts present in the reduced form, for example iron (2) sulfateheptahydrate, etc., giving redox systems.

In the case of the gel polymerization, the water-soluble azo initiatorsmay be initiated either thermally or else photochemically. A combinationof both is preferred.

It is also possible to use other auxiliaries, such as molecular weightregulators, e.g. thioglycolic acid, mercaptoethanol, formic acid, andsodium hypophosphite.

It can sometimes be necessary to obtain polymers with a high degree ofpolymerization and a low degree of crosslinking, since these parametershave a decisive effect on the water-retention capability and high andconstant viscosity.

This is successful by way of the preferred gel polymerization when thepolymerization is carried out at low reaction temperatures and with asuitable initiator system. A conversion of ≧99% can be achieved via thecombination of two initiator systems (azo initiators and redox system)which are first initiated photochemically at low temperatures and theninitiated thermally due to the exothermic nature of the polymerization.

Rapid drying under mild conditions avoids crosslinking side reactionsand provides constant product quality.

The associatively thickening monomers of the unit d) are moreover neededat at least 0.3 mol %, since they have a major effect on the propertiesof the gel block.

The hydrophobic monomers harden the gel block sufficiently to improveits ease of comminution. Combination with a release agent (e.g. Sitren595 from Goldschmidt) moreover prevents caking of the gel granules.

The flowable gel particles are therefore easier to distribute on adrying grid. This makes the drying process easier and indeed the dryingtimes can be shortened.

The gel polymerization preferably takes place at from −5 to 50° C., theconcentration of the aqueous solution preferably being adjusted to from40 to 70% by weight. To carry out the polymerization in one preferredembodiment, the sulfoalkylacrylamide in the form of its commerciallyavailable acid form is dissolved in water, neutralized by adding analkali metal hydroxide, and mixed, with agitation, with other monomersto be used according to the invention, and also with buffers, molecularweight regulators, and other polymerization auxiliaries. Once the pH hasbeen adjusted, preferably being from 4 to 9, the mixture is flushed withan inert gas, such as helium or nitrogen, and that is followed byheating or cooling to the appropriate polymerization temperature. If thechosen embodiment is gel polymerization without agitation, preferredlayers of thickness from 2 to 20 cm, in particular from 8 to 10 cm, arepolymerized under adiabatic reaction conditions. The polymerization isinitiated by adding the polymerization initiator and by irradiation withUV light at low temperatures (from −5 to 10° C.). Once the monomers havebeen completely converted, the polymer is comminuted using a releaseagent (Sitren 595 from Goldschmidt) in order to provide a larger surfacearea to accelerate drying.

The dried copolymers are in dried form when used according to theinvention. Since the reaction conditions and drying conditions are verymild, crosslinking side-reactions can be avoided, and polymers aretherefore obtained which have a very low gel content.

In another preferred embodiment, the copolymerization is an inversesuspension polymerization of the aqueous monomer phase in an organicsolvent. The procedure here is preferably that the monomer mixturedissolved in water and, where appropriate, neutralized is polymerized inthe presence of an organic solvent in which the aqueous monomer phasehas no, or low, solubility. Operations are preferably carried out in thepresence of “water in oil” emulsifers (W/O emulsifiers) and/orprotective colloids based on low- or high-molecular-weight compounds,used in proportions of from 0.05 to 20% by weight, based on themonomers. Examples of these stabilizers are hydroxypropylcellulose,ethylcellulose, methylcellulose, cellulose acetate butyrate mixedethers, copolymers of ethylene and vinyl acetate, styrene and butylacrylates, polyoxyethylene sorbitan monooleate, -laurate, or -stearate,block copolymers of propylene oxide and ethylene oxide, etc.

Examples of organic solvents which may be used are linear aliphatichydrocarbons, such as n-pentane, n-hexane, n-heptane, branched aliphatichydrocarbons (isoparaffins), cycloaliphatic hydrocarbons, such ascyclohexane and decalin, and also aromatic hydrocarbons such as benzene,toluene, and xylene. Other suitable materials are alcohols, ketones,carboxylic esters, nitro compounds, halogenated hydrocarbons, ethers,and many other solvents. Preference is given to organic solvents whichform azeotropic mixtures with water.

The water-soluble or water-swellable copolymers are initially producedin solution in the form of finely dispersed aqueous droplets in theorganic suspension medium, and are preferably isolated in the form ofsolid spherical particles in the organic suspension medium, by removingthe water. After removal of the suspension medium and drying, a granularsolid remains and is used according to the invention either directly orafter grinding.

The polymer compounds of the invention have excellent suitability asadditives for aqueous construction-material systems which comprisehydraulic binders, such as cement, lime, gypsum, anhydrite, etc. Theyare also useful in water-based paint systems and water-based coatingsystems.

The amounts preferably used of the copolymers of the invention depend onthe type of use and are from 0.05 to 5% by weight, based on the dryweight of the construction-material system, paint system, or coatingsystem.

The copolymers have excellent water-retention properties, even atrelatively high usage temperatures, and provide excellent performancecharacteristics for pigmented paints, renders, adhesive mortars,troweling compounds, joint fillers, spray concrete, underwater concrete,petroleum-drilling cements, etc., both during use and in the hardened ordried state. A particular feature of the polymers is that, even at highelectrolyte concentration, they can be used in the construction-materialmixtures for precise adjustment of thickening properties via chainlength, charge density, amphiphilic character, and hydrophobic sidechains. In concrete and self-leveling screeds and other flowableleveling compounds, small added amounts of the polymers serve asstabilizers and antisegregation agents.

Water-soluble or water-swellable copolymers containing sulfo groups andbased on (meth)acrylamide alkylsulfonic acids and (meth)acrylamide orN-vinyl compounds are described, as is their use as additives foraqueous construction-material systems or for water-based paint systemsand water-based coating systems. The copolymers of the invention arehighly effective and compatible water-retention agents in theseconstruction-material systems and paint systems, even when the amountsused are relatively small.

The following examples are intended to provide illustration of theinvention.

EXAMPLES Example 1 Gel Polymerization

400 g of water form an initial charge in a 11 three-necked flask withstirrer and thermometer. 87 g of flaked sodium hydroxide are dissolved,with stirring, and 450 g (2.17 mol) of2-acrylamido-2-methylpropane-sulfonic acid are slowly added and stirreduntil a clear solution is obtained. After addition of 0.50 g of citricacid hydrate, with 5% strength by weight aqueous sodium hydroxidesolution is added with stirring and cooling, and a pH of 4.60 isestablished. 83 g (0.83 mol) of N,N-dimethylacrylamide, 55 g (0.12 mol)of [2-(methacrylamido)-propyl]trimethylammonium chloride (50% strengthby weight solution in water), and 8.6 g of (0.023 mol)tristyrylpolyethylene glycol 1100 methacrylate (Sipomer SEM 25 fromRhodia; having 25 ethylene glycol units) were then added in succession,whereupon the pH fell to 3. The solution was adjusted to pH=6.0 using20% strength sodium hydroxide solution and inertized by flushing withnitrogen for 30 minutes, and cooled to about 5° C. The solution istransferred to a plastic container with dimensions (w*d*h) 15 cm*10cm*20 cm, and then 150 mg of2,2′-azobis(2-amidinopropane)dihydrochloride, 1.0 g of 1% Rongalitsolution, and 10 g of 0.1% strength tert-butyl hydroperoxide solutionwere added in succession. The polymerization is initiated by irradiationwith UV light (two Philips tubes; Cleo Performance 40 W). After about2-3 h, the hard gel is removed from the plastic container and cut intogel cubes of dimensions about 5 cm*5 cm*5 cm, using scissors. Prior tocomminution of the gel cubes by means of a conventional mincer, they arecoated with the release agent Sitren 595 (polydimethylsiloxane emulsion;Goldschmidt). The release agent is a polydimethylsiloxane emulsion whichwas diluted 1:20 with water.

The resultant granulated gel is distributed uniformly on drying gridsand dried in a circulating-air drying cabinet at from about 90 to 120°C. in vacuum, to constant weight.

This gave about 500 g of hard white granules, which were pulverized withthe aid of a centrifugal mill.

Example 2 Inverse Suspension Polymerization

200 g of cyclohexane and 1.50 g of ethylcellulose (ethoxyl content about48.5%, degree of substitution about 2.50) formed an initial charge in a500 ml four-necked flask with thermometer, stirrer, reflux condenser,and inert gas attachment. After 30 minutes of inertization, the reactorcontents were brought to the reflux temperature of 80° C., and anaqueous solution of 38.80 g (0.1872 mol) of2-acrylamido-2-methyl-propanesulfonic acid, 6.30 g (0.0636 mol) ofN,N-dimethylacrylamide, 4.05 (0.0092 mol) of[3-(methacryloylamino)propyl]trimethylammonium chloride (50% by weightin water), 1.1 g (0.003 mol) of tristyrylpolyethylene glycol 1100methacrylate (SEM 25), 35.95 g of 20% strength by weight aqueous sodiumhydroxide solution, 0.012 g of 2,2′-azobis(2-amidinopropane)dihydrochloride, and 5 g of water were added over a period of one hour.After the addition had ended, vigorous stirring was continued at from 75to 80° C. for a further 2.5 hours, and the water was then removedazeotropically over a period of about 2 hours. After cooling to roomtemperature, the solid was filtered off in the form of sphericalparticles, washed with a little cyclohexane, and dried in vacuo.

This gave 54.3 g of fine glassy granules which were ground to give afine white powder.

Other Examples

The procedure was carried out as described in Example 1 (gelpolymerization), but using the polymerization mixture given in Table 1:

TABLE 1 Monomer unit Sodium hydroxide a) solution Water b) c) d) YieldExample 3 2-Acrylamido- 50% strength Acrylamide [2-(Methacrylamido)-Tristyrylpoly- 2-methylpropane by weight (50% propyl]trimethyl- ethyleneglycol sulfonic acid aqueous sodium strength ammonium chloride 1100methacrylate hydroxide in water) (50% by weight in (SEM 25) solutionwater) 343.00 g 132.50 g 224 g 246.00 g 49.0 g 8.6 g 530 g (1.66 mol)(1.73 mol) (0.11 mol) (0.023 mol) Example 4 2-Acrylamido- 50% strengthN,N- [2-(Methacrylamido)- Tristyrylpoly- 2-methylpropane by weightDimethyl- propyl]trimethyl- ethylene glycol sulfonic acid aqueous sodiumaminopropyl ammonium chloride 1100 methacrylate hydroxide acrylamide(50% by weight in (SEM 25) solution water) 343.00 g 132.50 g 224 g 83 g49.0 g (0.11 mol) 8.6 g 510 g (1.66 mol) (0.52 mol) (0.023 mol) Example5 2-Acrylamido- 50% strength N,N- N,N-Dimethyl- Tristyrylpoly-2-methylpropane by weight Dimethyl- diallylammonium ethylene glycolsulfonic acid aqueous sodium acrylamide chloride 1100 methacrylatehydroxide (60% strength) (SEM 25) solution 343.00 g 132.50 g 224 g 83 g48.0 g 8.6 g 502 g (1.66 mol) (0.83 mol) (3.7 mol) (0.023 mol) Example 62-Acrylamido- 50% strength N,N- [2-(Acrylamido)- Tristyrylpoly-2-methylpropane by weight Dimethyl- propyl]trimethyl- ethylene glycolsulfonic acid aqueous sodium aminopropy ammonium chloride 1100methacrylate hydroxide acrylamide (60% by weight in (SEM 25) solutionwater) 338.00 g 130.50 g 300 g 135.00 g 90.0 g 6.5 g 530 g (1.63 mol)(0.85 mol) (0.27 mol) (0.0023 mol) Example 7 2-Acrylamido- 50% strengthN,N- N,N-Dimethyl- Behenylethylene 2-methylpropane by weight Dimethyl-diallylammonium glycol 1100 sulfonic acid aqueous sodium acrylamidechloride methacrylate hydroxide (60% strength) (Sipomer BEM; solutionRhodia) 343.00 g 132.50 g 224 g 83 g 48 g 5.3 g 502 g (1.66 mol) (0.83mol) (3.7 mol) (0.0017 mol) Example 8 2-Acrylamido- 50% strength N,N-N,N-Dimethyl- Tristyrylpoly- 2-methylpropane by weight Dimethyl-diallylammonium ethylene glycol sulfonic acid aqueous sodium acrylamidechloride 1100 methacrylate hydroxide (60% strength) (SEM 25) solution343.00 g 132.50 g 224 g 83 g 48 g 19.5 g 502 g (1.66 mol) (0.83 mol)(3.7 mol) (0.0069 mol) Example 9 2-Acrylamido- 50% strength N,N-Methacrylamido- Tristyrylpoly- 2-methylpropane by weight Dimethyl-propyldimethyl- ethylene glycol sulfonic acid aqueous sodium acrylamideammonium 1100 methacrylate hydroxide sulfobetaine (MAAB) (SEM 25)solution 334.00 g 129.0 g 381 75 g 75.0 g 6.0 g 502 g (1.61 mol) (0.74mol) (0.28 mol) (0.0021 mol) Comparative 2-Acrylamido- 50% strength N,N-[2-(Methacrylamido)- Methylpoly- Example 1 2-methylpropane by weightDimethyl- propyl]trimethyl- ethylene glycol sulfonic acid aqueous sodiumacrylamide ammonium chloride 1100 methacrylate hydroxide solution 343.00g 132.50 g 224 g 83 g 49.0 g 3.97 g 502 g (1.66 mol) (0.52 mol) (0.11mol) (0.0047 mol)

Comparative Example 2 Inverse Suspension Polymerization

Using a method based on Example 2, a mixture of the followingcomposition was polymerized by the inverse suspension polymerizationprocess:

An aqueous solution of 38.80 g (0.1872 mol) of2-acryl-amido-2-methylpropanesulfonic acid, 6.30 g (0.0636 mol) ofN,N-dimethylacrylamide, 4.05 (0.0092 mol) of[3-(methacryloylamino)propyl]trimethylammonium chloride (50% by weightin water), 1.99 g (0.004 mol) of methylpolyethylene glycol 500 monovinylether, 35.95 g of 20% by weight aqueous sodium hydroxide solution, 0.012g of 2,2′-azobis(2-amidinopropane) dihydrochloride, and 5 g of water isadded to the organic solvent.

The usual drying and work-up gave 51.2 g of fine glassy granules, whichwere ground to give a fine white powder.

Comparative Example 3

Commercially available methylhydroxypropylcellulose with a solutionviscosity of 790 mm²/s (measured in the form of a 1% strength aqueoussolution at 20° C. by the Ubbelohde method).

Table 2 gives the comminution properties and the necessary drying times.It is clearly seen that incorporation of the unit c) into the polymerspermits milder drying conditions and shorter drying times in comparisonwith Comparative Example 1. The residual moisture level of the groundpowder is a measure of the extent of completion of the drying process.

The gel content of the polymer is defined as the insoluble gel particlesproduced by side reactions during the polymerization or the dryingprocess. To determine this, 1 liter of a 0.1% strength aqueous solutionis prepared. The solution is poured onto a metal screen (0.5 mm) andthen washed with 2 1 of water. The gel content remaining in the screenis transferred to a measuring cylinder and the volume is determined.

TABLE 2 Residual Drying moisture Gel Gel Temperature time level contentproperties [° C.] [min] [%] [ml] Example 1 very hard 80 100 3 30 smallparticles with good flowability Example 3 as in 80 90 5 50 Example 1Example 4 as in 120 60 8 80 Example 1 Example 5 as in 100 70 3 40Example 1 Example 6 as in 100 60 7 45 Example 1 Example 7 hard 80 100 560 flowable particles Example 8 very hard 80 70 5 55 the particles aremarkedly smaller than given for Example 1 Example 9 hard 80 65 5 40 theparticles are markedly smaller than given for Example 1 Example 2 4 150Comparative soft gel; 150 240 15 250 Example 1 difficult to comminute;the gel particles conglutinate again to give clumps Comparative 6 280Example 2

Table 3 gives solution viscosities of 0.5% strength aqueous solutions,with and without addition of 1 and 2% of sodium sulfate.

It is clearly seen that the viscosities of the polymer solutions whenelectrolyte is added are higher in comparison with the comparativeexample, although the viscosities without salt addition are at the samelevel. The more of the associatively thickening monomer incorporated inthe polymer, the smaller the fall in the viscosity under the action ofelectrolyte. Example 5 also shows lower electrolyte sensitivity incomparison with Example 1.

TABLE 3 [mPAS*s}* Viscosity of Viscosity of 0.5% strength 0.5% strengthViscosity of soln. with 1% soln. with 2% 0.5% strength of sodium ofsodium soln. sulfate sulfate Example 1 3557 1332 1230 Example 2 25121005 988 Example 3 3250 1198 1058 Example 4 2400 1056 987 Example 5 36412132 2102 Example 6 2631 1156 1104 Example 7 3868 2563 2498 Example 84531 4690 4720 Example 9 3738 3645 3701 Comparative 3747 106 87 Example1 Comparative 2280 45 62 Example 2 *20° C., Brookfield, in H₂O (Measuredat 5 revolutions per minute)

Application Examples

The performance-related assessment of the copolymers of the inventionused a tile-adhesive mortar test mixture.

This practical test used a ready-mixed dry formulation with theadditives of the invention or the comparative products admixed in solidform. Following drying mixing, a certain amount of water was added, andvigorous stirring was carried out (duration 2*15 seconds) by means of adrill with G3 mixer. The mixture with water was then permitted to agefor 5 min and was subjected to a first visual check. The standardizeddetermination of consistency (slump to DIN 18555, Part 2) then followedimmediately after the ageing period, and for a second time 30 min afterthe mixing with water (after brief manual stirring). Water retention isdetermined about 15 min after mixing with water to DIN 18555, Part 7.

The composition of the tile-adhesive mortar can be seen in Table 4.

The results obtained are presented in Tables 5 and 6.

TABLE 4 Composition of test mixture (in % by weight) Component AmountPortland cement 36.00¹⁾ Quartz sand (from 0.05 to 0.4 mm) 56.90 Whitepigment³⁾ 5.50 Cellulose fibers 0.50 Water-retention agent 0.16 ¹⁾CEM II42.5 R ³⁾Ulm white “Juraperle MHS”

TABLE 5 Usage properties of a ceramic-tile-adhesive mortar which wasmodified using polymers of the invention and polymers corresponding tothe prior art. Amount Slump Air of after pores Water Additive waterSlump 30 min (% by retention (Example No.) (g) (cm) (cm) volume) (%) 1260 14.9 15.1 13.0 99.1 2 260 16.6 17.2 15.8 97.9 3 260 15.0 15.5 14.298.5 4 260 19.8 19.6 12.7 98.2 5 260 15.0 15.1 13.7 99.5 6 260 19.6 19.615.9 98.0 7 260 14.5 14.7 16.9 98.3 8 260 13.2 13.7 16.1 99.4 9 260 14.314.5 15.3 99.2 Comparison 1 260 15.6 18.7 10.9 97.7 Comparison 2 26018.0 19.3 10 95.5 Comparison 3 260 17.0 17.3 10 97.3 Addition: 0.16% byweight Adhesive mortar: 1000 g

Finally, the water retention of the product of the invention was alsodetermined at an increased usage temperature of 40° C., and comparedwith the results of the testing of conventional cellulose-basedadditives. For this, the dry mortar, the water for mixing, and theapparatus used were heated to 40° C. by pretreating lasting 6 hours.Table 6 shows the results of these tests.

TABLE 6 Water retention of copolymers of the invention inmachine-rendering at an elevated temperature, in comparison with theprior art. 20° C. 40° C. Additive Water Slump WR* Slump WR* (ExampleNo.) (g) (cm) (%) (cm) (%) 1 260 14.3 98.9 13.7 99.1 4 260 19.1 98.418.7 98.6 5 260 14.9 99.0 14.1 99.2 7 260 14.1 98.8 13.5 98.8 8 260 13.599.3 13.9 99.0 9 260 14.5 99.1 14.7 98.9 Comparison 3 260 17.2 96.9 15.488.0 *Water retention (WR) Addition: 0.16% by weight Dry mortar: 1000 g

1. A water-soluble or water-swellable copolymer containing sulfo groupsand comprising a) from 3 to 96 mol % of units of formula I

wherein R¹ is hydrogen or methyl; R², R³, R⁴ are independently selectedfrom hydrogen, an aliphatic hydrocarbon radical having from 1 to 6carbon atoms, a phenyl radical, or a phenyl radical substituted withmethyl groups; M is hydrogen, a monvalent metal cation, a divalent metalcation, ammonium, or an organic amine radical; a is 0.5 or 1; b) from 3to 96 mol % of units of at least one of formula IIa and IIb

wherein W is —CO—, —CO—O—(CH₂)_(x)—, or —CO—NR²—(CH₂)_(x)—wherein x isfrom 1 to 6; R⁵ and R⁶ are independently selected from hydrogen, aC₁-C₂₀ substituted aliphatic hydrocarbon radical, a C1-C20 unsubstitutedaliphatic hydrocarbon radical, a C5-C8 cycloaliphatic hydrocarbonradical, a C6-C14 aryl radical; and Q is hydrogen or —CHR⁵R⁷; R⁷ ishydrogen, an aliphatic hydrocarbon radical having from 1 to 4 carbonatoms; —COOH or —COO—M_(a), and R¹, R², M and a are as defined above;wherein if Q is not hydrogen, R⁵ and R⁶ in IIb can together form a—CH₂—(CH₂)_(y)-methylene group where y is from 1 to 4; c) from 0.05 to75 mol % of units of at least one of formulas IIIa and IIIb

wherein Y is O, NH or NR⁵; V is —(CH2)_(x)—,

R⁸ is R⁵, R⁶, —(CH₂)_(x)—SO₃ ⁻(M),

and X is halogen, a C₁-C₄-alkyl sulfate or a C₁-C₄-alkylsulfonate; R¹,R², R³, R⁵, R⁶, and x are as defined above; and d) from 0.01 to 30 mol %of units of formula IV

wherein Z is —COO(C_(m)H_(2m)O)_(n)—R⁹, —(CH₂)_(p)—O(C_(m)H_(2m)O)_(n)—R⁹, wherein R⁹ is a saturated or unsaturated, linearor branched, aliphatic hydrocarbon radical having from 22 to 40 carbonatoms, or

R¹⁰ is H, C₁-C₄-alkyl-, phenyl-, benzyl-, C₁-C₄-alkoxy, halogen, cyano,—COOH, —COOR⁵, —CO—NH₂, or —OCOR⁵; R¹¹ is an arylalkyl group having aC₁-C₁₂-alkyl radical and a C₆-C₁₄-aryl radical; m is from 2 to 4; n isfrom 0 to 200; p is from 0 to 20; and R¹ and R⁵ are as defined above,wherein the copolymer is water-soluble or water swellable and containssulfo groups.
 2. The copolymer as claimed in claim 1, wherein themono-or bivalent metal cation is selected from the group consisting of asodium ion, a potassium ion, a calcium ion, and a magnesium ion.
 3. Thecopolymer as claimed in claim 1, wherein the organic amine radicals areselected from the group consisting of substituted ammonium groups whichare derived from primary, secondary, or tertiary C₁-C₂₀-alkylamines,C₁-C₂₀-alkanolamines, C₅-C₈-cycloalkylamines, and C₆-C₁₄-arylamines. 4.The copolymer as claimed in claim 1, wherein the hydrocarbon radicals oraryl radicals of R⁵ and R⁶ are also substituted with at least one ofhydroxyl, carboxyl, and sulfonic acid.
 5. The copolymer as claimed inclaim 1, wherein X is selected from the group consisting of chlorine,bromine, sulfate, and methyl sulfate.
 6. The copolymer as claimed inclaim 1, comprising from 40 to 80 mol % of unit a), from 15 to 55 mol %of unit b), from 2 to 30 mol % of unit c), and from 0.5 to 10 mol % ofunit d).
 7. The copolymer as claimed in claim 1, having a number-averagemolecular weight of from 50,000 to 10,000,000.
 8. A method for preparingthe copolymers of claim 1, comprising polymerizing the copolymer byaqueous solvent polymerization, gel polymerization or an inversesuspension polymerization in organic solvents at temperatures of from−20 to 250° C., with free-radical initiators and optionally polymerizingauxiliaries.
 9. The method as claimed in claim 8, wherein the aqueoussolvent polymerization takes place at from 5 to 120° C.
 10. The methodas claimed in claim 8, wherein the pH ranges from 4 to
 9. 11. The methodas claimed in claim 8, wherein the aqueous gel polymerization is carriedout at a temperature of from −5 to 50° C.
 12. The method as claimed inclaim 11, wherein the gel polymerization, the free-radical initiation isselected from thermal and photochemical.
 13. The method as claimed inclaim 11, wherein the gel polymerization is conducted without agitationin layers of polymerization solution of thickness from 2 to 20 cm. 14.The method as claimed in claim 11, wherein the resultant gel iscomminuted.
 15. The method as claimed in claim 8, wherein the inversesuspension polymerization is carried out in an organic solvent in thepresence of at least one of a water-in-oil emulsifier or a protectivecolloid.
 16. The method as claimed in claim 15, wherein the proportionsof the at least one water-in-oil emulsifier or protective colloid arepresent in an amount of from 0.05 to 20% by weight, based on themonomers.
 17. The method as claimed in claim 15, wherein the organicsolvent comprises at least one of an aliphatic, cycloaliphatic andaromatic hydrocarbon.
 18. A construction material comprising thecopolymer as claimed in claim 1 and an hydraulic binder.
 19. A paintcomprising the copolymers as claimed in claim 1, water and pigment paintsystems and water-based coating systems.
 20. The construction materialas claimed in claim 18, comprising from 0.05 to 5% by weight of thecopolymer, based on the dry weight of the construction-material system.21. The copolymer as claimed in claim 2, wherein the organic amineradicals are substituted ammonium groups from at least one of a primary,secondary, or tertiary C₁-C₂₀-alkylamine, a C₁-C₂₀-alkanolamine, aC₅-C₈-cycloalkylamine, or a C₆-C₁₄-arylamine.
 22. The method as claimedin claim 12, wherein the gel polymerization is undertaken withoutagitation in layers of polymerization solution of thickness from 2 to 20cm.
 23. The method as claimed in claim 16, wherein the organic solventcomprises at least one of an aliphatic, cycloaliphatic or aromatichydrocarbon.
 24. The paint as claimed in claim 19, wherein the amount ofthe copolyrner ranges from 0.05 to 5% by weight, based on the dry weightof the paint.
 25. A coating system comprising the copolymer of claim 1and a coating material.
 26. The coating system of claim 25, comprising0.05 to 5% by weight of the copolymer based on dry weight.
 27. Themethod of claim 14, wherein the resultant gel is comminuted with the aidof a release agent.